DevTool Demo Virtual IMU

• An IMU is malfunctioning, and you’ve been tasked with developing an algorithm to replace this sensor dependency.
• You wish to develop and test this within SOLIS.

• The purpose of this tutorial is to demonstrate the concepts that are required to develop custom logic; not to arrive at a fully-robust algorithm to meet the objective.
• With this knowledge, you will be well on your way to solving any customization idea.
• SOLIS and MAX are very valuable tools for developing such an algorithm, due to the rapid cycles of design, implementation, and testing.
  • This is true regardless of the final Flight Software chosen to implement within.

A completed instance of this demo is provided in the delivered SOLIS Example Scenarios

• Distributed via the SOLIS 12.0 installer C:\ProgramData\AGI\STK 12\SOLIS\ExampleScenarios\SOLISExample_DevToolDemo_Virtual_IMU

To begin a new instance of this demo

1. Make the new directory: C:\ProgramData\AGI\STK 12\SOLIS\DevToolDemo_Virtual_IMU
2. Copy the contents of: C:\ProgramData\AGI\STK 12\SOLIS\ExampleScenarios\SOLISExample_DevToolDemo_Virtual_IMU\_FreshDemoContent into C:\ProgramData\AGI\STK 12\SOLIS\DevToolDemo_Virtual_IMU
3. Open STK Scenario: C:\ProgramData\AGI\STK 12\SOLIS\DevToolDemo_Virtual_IMU\SOLISExample_Landmapper_BC.sc
4. Open SOLIS on the Landmapper_BC satellite within this scenario

In SOLIS click the button to get started. Default values are all that is needed for this project.

Save setting to RunDevTool_Virtual_IMU.bat file for easy running of the DevTool next time.

Click on the Run DevTool button to run the DevTool. This will generate a Visual Studio solution, ready for your custom development.

The solution will build successfully “out of the box"

After building, hit on the SOLIS GUI and you will see the DLL with a timestamp. This is an indication that SOLIS is linked with the Virtual_IMU.

A search for “IMU” reveals the FSW_SenProc_IMU interface.

• This interface embeds the FSW_SenProc_RTE interface, which we see contains a VECTOR of Rate_BDY_rdps.

To confirm FSW_SenProc_RTE is what we want, a search for “Determination” in ADCS_FSW.xml shows this is the connection to the AD.

Recalling from our conceptual design, we’d like our new Virtual_IMU to produce this RTE interface. This is done using the <BaseInterface Name="FSW_SenProc_RTE"/> tag.

<?xml version="1.0" encoding="utf-8"?> <Extension xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="MAXDevToolSchema.xsd" xmlns="asi_mc"> <SettingsDefinition> <FileHeader> ============================================================================ A custom algorithm demonstration ============================================================================ </FileHeader> </SettingsDefinition> <ComponentDefinition Name="Virtual_IMU"> <BaseInterface Name="FSW_SenProc_RTE"/> </ComponentDefinition> </Extension>

Run the DevTool using the RunDevTool_Virtual_IMU.bat

You should now see new files in your Virtual_IMU solution. Around line 141 within Virtual_IMU.cpp you will see the return function that will provide rate data across our FSW_SenProc_RTE interface.

Using the search concepts from adding the RTE Interface, we bring Star Tracker Data into the Virtual IMU using the <Configuration><Interface> Tag in the XML.

Write the XML shown below and run the RunDevTool_Virtual_IMU.bat

Start of file:

<?xml version="1.0" encoding="utf-8"?> <Extension xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="MAXDevToolSchema.xsd" xmlns="asi_mc"> <SettingsDefinition> <FileHeader> ============================================================================ A custom algorithm demonstration ============================================================================ </FileHeader> </SettingsDefinition> <ComponentDefinition Name="Virtual_IMU"> <BaseInterface Name="FSW_SenProc_RTE"/>

Add <Configuration> and <Interface>:

<Configuration> <Interface InterfaceType="FSW_SenProc_ADSensor" Description="Pull in the CBI2BDY quaternion from the Star Tracker"/> </Configuration>

Rest of the file:

</ComponentDefinition> </Extension>

Access to our Star Tracker data within the Virtual IMU

Within Virtual_IMU.cpp, you should now be able to access the m_Connection structure.

Write the following two lines, providing access to our Star Tracker data within the Virtual IMU component

bool str_Valid = m_Connection.FSW_SenProc_ADSensor_ptr->GetIsValid(); QUATERNION str_QCBI2BDY = m_Connection.FSW_SenProc_ADSensor_ptr->GetSensedQuaternion_CBI2BDT();

<?xml version="1.0" encoding="utf-8"?> <Extension xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="MAXDevToolSchema.xsd" xmlns="asi_mc"> <SettingsDefinition> <FileHeader> ============================================================================ A custom algorithm demonstration ============================================================================ </FileHeader> </SettingsDefinition> <ComponentDefinition Name="Virtual_IMU"> <BaseInterface Name="FSW_SenProc_RTE"/> <!-- A local definition of an enumeration that will be used in parameters, commands, and telemetry --> <DefinedEnum Name="ERateSource"> <Enum Value="0" Text="IMU"/> <Enum Value="1" Text="Virtual_IMU"/> </DefinedEnum> <!-- This section represents all things that are set from configuration files --> <Configuration> <Interface InterfaceType="FSW_SenProc_ADSensor" Description="Pull in the CBI2BDY quaternion from the Star Tracker"/> <Interface InterfaceType="FSW_SenProc_RTE" Description="Pull in the original IMU data"/> <EnumParameter Name="E_InitialRateSource" Enum="ERateSource" DefaultValue="0" Description="Initial rate source to use"/> <BasicParameter Name="D_MaxDeltaTimeForRate_s" Type="double" Units="sec" MinValue="0.0" DefaultValue="10.0" Description="Maximum time between STR measurements to compute the back-difference"/> </Configuration> <Commands> <Command Mnemonic="SETSOURCE" Description="Set the source of data to pass through"> <ComponentEnumArgument Name="Source" DefinedEnum="ERateSource" Description="Which source to pass through"/> </Command> </Commands> <Telemetry> <ComponentEnumItem Name="RateSource" DefinedEnum="ERateSource" Units="enum" Description="The currently selected rate source"/> <!-- Note: All telemetry is a single channel. The [X:Y:Z] syntax below is a macro to form 3 telemetry mnemonics (doubles) with one line of XML on the VECTOR--> <BasicItem Name="Rate_BDY[X:Y:Z]" LocalName="Rate_BDY_rdps" Type="VECTOR" Units="rad/s" Description="The computed virtual rate in the BDY [X:Y:Z] frame"/> </Telemetry> </ComponentDefinition> </Extension>

• Extension The root-level XML node, containing any number of component interface and/or definition descriptions.
  • SettingsDefinition Optional settings
  • ComponentDefinition A Core building block of adding software to augment MAX.
    • BaseInterface Defines the interface(s) that the Component will produce. In this case, we are producing the FSW_SenProc_RTE interface which will be used to send rate data to Attitude Determination.
    • DefinedEnum Defines an enumeration local to this component. We will utilize this enumeration within a parameter, command, and telemetry, as we switch the source of the rate signal output.
    • Configuration
      • Interface Defines the interface(s) that this component needs to get data from. In this case, we are getting data from the IMU and the Star Tracker.
      • EnumParameter & BasicParameter Used to create parameters into the system that are defined within the Configuration files (*.cfg).
    • Commands Defines the commands. In this case, we have one command that has an input argument to change the rate source.
    • Telemetry Defines the telemetry data (to STK Data Provider and/or to CSV) from this component.

Virtual_IMU.hpp

We will need to define a couple variables, in the “private” section.

double m_PrevTime_s; QUATERNION m_PrevQ_CBI2BDY;

Virtual_IMU.cpp

Initialize the new variables.

void CVirtual_IMU::CommonConstructor(void) { m_PrevQ_CBI2BDY = C_QId; m_PrevTime_s = 0.0; }

At the bottom of Init() – Initialize the RateSource telemetry to the initial parameter.

m_Tlm.RateSource = m_Parm.E_InitialRateSource;

Within GetRate_BDY_rdps() – Return the computed rate across the FSW_SenProc_RTE interface.

const VECTOR CVirtual_IMU::GetRate_BDY_rdps(void) { return m_Tlm.Rate_BDY_rdps; }

Within GetMeasRateValid() – Return rate always valid (simplified assumption for now)

Hardware::E_SenMeasValidity CVirtual_IMU::GetMeasRateValid(void) { return Hardware::E_ValidThisFrame; }

Within AcceptCmd_SETSOURCE() – Update the RateSource to the command argument

E_FSW_STATUS CVirtual_IMU::AcceptCmd_SETSOURCE(const SETSOURCE_CMD_STRUCT* arguments ) { m_Tlm.RateSource = arguments->Source; return E_FSW_OK; }

int CVirtual_IMU::ProcessInputs(void) { int Ret = 0; // Setup a switch statement that either passes the raw IMU signal through, or computes the rate from the Star Tracker. switch (m_Tlm.RateSource) { case ERateSource::E_IMU: // In this case, just pass through what the IMU reported m_Tlm.Rate_BDY_rdps = m_Connection.FSW_SenProc_RTE_ptr->GetRate_BDY_rdps(); break; case ERateSource::E_Virtual_IMU: // This is where we will perform calculations to form a rate estimate from the Star Tracker // If the Star Tracker is valid, get the data from it to use for upcoming calculations. if (m_Connection.FSW_SenProc_ADSensor_ptr->GetIsValid()) // Star Tracker has a new measurement { QUATERNION str_Q_CBI2BDY = m_Connection.FSW_SenProc_ADSensor_ptr->GetSensedQuaternion_CBI2BDY(); double str_CurrentTime_s = m_Connection.FSW_SenProc_ADSensor_ptr->GetLastValidTime_SCLK_s(); double thisDeltaTime_s = str_CurrentTime_s - m_PrevTime_s; // If we have a new measurement that is within a parameterized time of an old good measurement, compute the quaternion difference and get the rate. if (thisDeltaTime_s < m_Parm.D_MaxDeltaTimeForRate_s && thisDeltaTime_s > EPSILON) { QUATERNION qDelta; Math_Qinv_Q_Mult(m_PrevQ_CBI2BDY, str_Q_CBI2BDY, qDelta); // Calculate Delta Angles using small-angle approximation VECTOR deltaAng_rd = 2.0 * Math_Sign(qDelta[3]) * VECTOR(qDelta[0], qDelta[1], qDelta[2]); // Determine Rate by back-differencing the quaternion m_Tlm.Rate_BDY_rdps = deltaAng_rd / thisDeltaTime_s; } // Setup the persistence variables for the next back-difference m_PrevTime_s = str_CurrentTime_s; m_PrevQ_CBI2BDY = str_Q_CBI2BDY; } break; } return Ret; }

Create a Copy of our SOLIS-Generated Configuration Set, named WithVirtual_IMU

Create an instance of our Virtual_IMU component, configured as-shown

• Priority 315 defines when this component executes, relative to other priorities. We place it between FSW_SenProc_IMU (310) and FSW_AttDetermination (600). The Configuration Overview button provides a table of all Components and their priorities.
• Master ID 315 defines the command and telemetry APID (Application ID). This must be unique from other APIDs
• Be sure the Output File goes into FSW_Components.cfg. An error would occur if this goes into the ODY_* cfg files

Add (or edit) Connections to the Virtual_IMU

• We want the Virtual_IMU to get data from the FSW_SenProc_IMU and FSW_SenProc_STR_Sinclair_STR.

Similar to the Connections section, the Parameters can be defined

• If not specified, they will default to the DefaultValue specified in the XML.
• If the XML did not specify a DefaultValue, the value will be zero.

Since we need to modify the Attitude Determination, create a Copy of the FSW_AttDetermination

• The default copy parameters are good, just change the Version Name to WithVirtual_IMU.

Now we need to modify the Connection_FSW_SenProc_RTE

• Select the 2nd row in the Connections section.
• Click the edit icon.
• Change the Connected Component to Virtual_IMU.
• Change the Accessor to FSW_SenProc_RTE.
  • Not Connection_FSW_SenProc_RTE, as this is the accessor to the input IMU.

Select WithVirtual_IMU as the Active Configuration Set

• This tells SOLIS to write the Configuration files as you’ve set them up within that set, with our new Virtual IMU.

Add the new Custom/Virtual_IMU packet to the recorded telemetry

• Start the simulation running 10x realtime
• Using the Real-Time Commanding feature, issue our new Custom command to change the Rate Source
• Next, issue a Slew Relative command to cause the Star Tracker to point toward the Earth
• Lastly, run the GoTo Hold command timed while the Star Tracker Field of View is not intersecting Earth

Telemetry results can be seen using the STK Data Provider. All SOLIS data will be under the User Supplied Data section, with our new Virtual IMU telemetry under the Custom folder.

Below shows the results of this simulation. At ~152 seconds the command was issued to start using the Virtual_IMU rate solution. This held together until the slew was commanded that now blocked the star tracker. The system ultimately recovered after the GoTo Hold command was issued at ~450 sec.